Humminbird SmartCast RF10 Mobile Station 4-Inch Waterproof Fishfinder 100-foot radius operating range with 100 ft. depth capability, ultra-wide coverage equal to twice your depth Lightweight, compact, and totally waterproof display, with a backlight for night fishing 1-touch menu navigation easily controls fish ID, depth range, fish alarm, and sensitivity Fully waterproof remote sonar sensor typically lasts for 400 hours of in-the-water usage Wet Switch technology maximizes battery life by automatically shutting down when the remote sonar sensor is out of water